Lord Justice Leveson is the high court judge charged with heading the inquiry into the phone-hacking scandal.

But his brief goes much further than that, a two-pronged investigation into the "culture, practices, ethics of the press" and the "extent of unlawful or improper conduct within News International and other organisations", as well as the "extent to which the police received corrupt payments or were otherwise complicit in such misconduct".

The inquiry will take in broadcasting and social media as well as the press and could lead to stricter cross-media ownership regulation.

No wonder Nick Clegg, who pressed David Cameron to put a judge in charge of the inquiry and is a fellow new entry in this year's MediaGuardian 100, called it a "once-in-a-generation chance to clean up the murky underworld of the corrupted relationship between the police, politics, and the press".

Leveson made his name as a prosecutor, most notably in the 1995 trial of Rose West, Britain's most prolific female serial killer. He also conducted the prosecution of Ken Dodd for tax evasion. The comedian was acquitted.

"The press provides an essential check on all aspects of public life," he said after his appointment. "That is why any failure within the media affects all of us. At the heart of this inquiry, therefore, may be one simple question: who guards the guardians?"

His inquiry is expected to be completed within 12 months, and will have the power to summon witnesses including journalists, newspaper executives, media barons, policemen and politicians to give evidence under oath and in public.

He will be assisted by a panel of six senior independent figures with relevant experience in media, regulation and government.

"The inquiry he is about to head into phone hacking and media standards will demand a rigorous focus," said a Guardian editorial.

"Its draft terms of reference are extraordinarily broad; a weak chair would soon become lost amid the many demands being placed on his panel and his investigation might become tangled in the long grass. A cynic might even wonder if that was not the expectation."

As chairman of the Sentencing Council, he is also responsible for the politically sensitive issue of drawing up guidelines for the courts. Earlier this year the Sun labelled him a "softie" for his stance on sentencing criminals. Who's the softie now?